title: Rural population estimates: an analysis of a large secondary data set.
abstract: OBJECTIVE
  Health services research often utilizes secondary data sources such as the Behavioral Risk Factor Surveillance System (BRFSS). Since 2006, the released BRFSS data do not include respondents who live in counties with 10,000 or fewer residents, and the CDC no longer offers the opportunity to access the unrestricted data set. As a result, rural residents can be underrepresented in BRFSS data after 2005. The purpose of this analysis is to examine the potential for bias introduced by rural underestimation.
  
  
  METHODS
  We utilized 6 BRFSS data sets; the 2005 full data and the 2005-2009 restricted data. We estimated population sizes for each survey year, and we compared these estimates to comparable data from the US Census intercensal estimates. We also compared estimates of preventive service utilization (mammography, Pap tests, colorectal cancer screening, and influenza vaccinations) between the two 2005 data versions.
  
  
  RESULTS
  Rural populations were underrepresented, particularly with the smaller counties excluded. Remote rural residents were the most consistently underrepresented. Preventive service delivery estimates differed between the full and restricted 2005 data versions. Mammography and Pap test estimates tended to be higher in the restricted data, while colorectal cancer screening and influenza vaccinations were similar or inconsistent. These results indicate that restricting by county size introduced bias in these estimates.
  
  
  CONCLUSIONS
  Having quality, nationally representative data is important to study disparities in service delivery. The potential bias introduced by the BRFSS county restriction may result in rural research being less effective for policy recommendations and interventions.
authors.affiliation: Department of Family and Preventive Medicine, University of South Carolina School of Medicine, Columbia, South Carolina, USA. Kevin.bennett@sc.edu
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Bennett
mesh_terms: D000328:Adult; D000368:Aged; D003710:Demography; D005260:Female; D006302:Health Services Research / Q000706:statistics & numerical data; D006306:Health Surveys; D054625:Healthcare Disparities; D006801:Humans; D008297:Male; D008875:Middle Aged; D019035:Rural Health Services / Q000706:statistics & numerical data*; D012424:Rural Population / Q000706:statistics & numerical data*; D013223:Statistics as Topic; D014481:United States; D055815:Young Adult